1. Field of the Invention
The present invention relates to a seek system for a magnetic disk processing apparatus having a patrol seek function.
2. Prior Art
Conventionally, a magnetic disk apparatus having a patrol seek function has been controlled by a firmware such as a flowchart of a magnetic disk processing apparatus as shown in FIG. 1 (a) and FIG. 1 (b). FIG. 1 (a) illustrates a main routine in which the condition of the magnetic disk is monitorred and the timer control is carried out for patrol seeking by polling operation (step 311), and for each period of time, a patrol seek control operation carries out the control of the patrol seek (step 312). If the I/O operation (a command for executing a chain of software instructions) is activated (step 313), then the processing is shifted to a command fetch/decode portion and, in accordance with the processing result therein, the command (software instruction) is actually executed by the command processing (steps 315 and 316). Then, after the chain of commands (hereinafter referred to as CC) is executed or a terminating operation is executed (steps 318 and 319) depending on whether the chain of commands (command chain) is present or not (step 317), the procedure is returned to the command processing or polling operation.
Next, FIG. 1 (b) illustrates a read command subroutine, which is part of the subroutine of the command execution shown in FIG. 1 (a). After a read command is issued to the magnetic disk apparatus in accordance with the read command processing (step 321), a physical address PA of data which has been read and a PA stored within the magnetic disk unit are compared with each other (step 32) and, if that result coincides with each other, then the command execution is continued and, if otherwise, an error processing is conducted.
In such a conventional magnetic disk processing unit, since the seek command is issued to the magnetic disk unit by patrol seeking independently of the command from the software, there occurs a mismatch between the PA of the magnetic disk unit, which is retained by the software and the magnetic disk processing unit, and the PA where the magnetic head actually lies, which, when the data of the magnetic disk unit is read from or written onto the magnetic disk unit in accordance with the command from the software, causes a track completely different from one of which the software is conscious (unit accessed by the magnetic disk unit which may be universally defined by the PA) to be accessed. In addition, in such a case, there is no method of determining by software whether the error has occurred due to the patrol seek or not and, depending on the case, a erroneous operation of the software can be incurred, which damages the system reliability.